Source: Planetarium Gold
Argo Navis, the Ship was once a huge constellation far to the south, backing across the sky, its stern beneath the hindquarters of Canis Major. Later it was split into three smaller more manageable groups - Puppis, the stern; Vela, the sail; and Carina, the keel.
Argos built the ship for young Jason to help him in his quest for the Golden Fleece. Jason gathered up fifty men - Hercules, Cepheus, Orpheus, Castor, and Pollus among them - to set out on a series of exploits that finally got them the fleece of Aries, the ram. Upon their return, the Goddess Athena placed Argo Navis in the sky, dedicating it to Neptune.
From North Star to Southern Cross by Will Kyselka & Ray Lanterman (Univ. of Hawaii Press, 1976)